9520335 Zimmerman Many studies suggest that the two most important factors limiting the reproductive success of birds are nest predation and food supply. It has recently been proposed that the combined effects of these two factors may act to limit nesting success through a conflict between the time parents allocate to foraging for nestlings and time needed to guard the nest from predators. Birds nesting in territories with an increased food supply should be able to devote more time toward guarding the nestlings from predators and therefore experience reduced levels of nest predation. In addition, birds nesting in areas with reduced predator abundance should be able to allocate more time toward foraging for nestlings and therefore increase reproductive success through greater fledgling mass and survivability. This research will test these time allocation hypotheses in a population of brown thrashers by simultaneously manipulating food supply and predation risk. Nesting success will be monitored and behavioral observations will be conducted to determine how parents allocate time to foraging and guarding behaviors when nesting in areas of increased food supply, reduced predation risk, or both. This research will enhance our understanding of the factors that shape avian foraging strategies and determine nesting success. Given the recent population decline in many bird species, the results may also contribute to attempts to conserve biodiversity.
